Fluid flow control system

ABSTRACT

A fluid flow control system ( 20 ) comprises a pumping assembly ( 22 ) for pumping a fluid ( 23 ) through an orifice ( 30 ), and a pressure measuring assembly ( 32 ) for measuring, and providing information on, the change in pressure across the orifice ( 30 ). The fluid flow control system ( 20 ) also includes a controller ( 36, 38 ) to adjust the pump assembly ( 22 ) in accordance with the aforesaid information and vary the rate of flow of the pumped fluid.

This invention relates to fluid flow control systems. This invention also relates to methods of controlling fluid flow. More particularly, but not exclusively, the invention relates to fuel flow control systems, and methods for controlling fuel flow, for example for the flow of fuel in a gas turbine engine.

Conventional fuel metering systems on gas turbine engines generally control the flow of fuel and require complex hydromechanical, electrical, electronic and software control loops to be implemented. These have cost, weight and reliability penalties.

According to one aspect of this invention, there is provided a fluid flow control system comprising a pumping assembly for pumping a fluid through an orifice, a pressure measuring assembly for measuring, and providing information on, the change in pressure across the orifice, and a controller for processing the aforesaid information to adjust the pump assembly in accordance with the aforesaid information and vary the rate of flow of the pumped fluid.

Preferably, the pumping assembly comprises a torque driven pumping assembly. The controller may be arranged to adjust the drive torque of the pump assembly in accordance with the aforesaid information on the change in pressure.

The pumping assembly may comprise a torque driven pump and a prime mover to create the torque for driving the pump. The prime mover may be a motor. The motor may be an electric motor. The prime mover may have a rotatable component to provide the aforesaid torque to the pump.

The fluid flow control system may comprise a main compensator to modify the aforesaid information to a form usable by the pumping assembly.

Preferably, the controller provides a control signal to the pumping assembly to effect the aforesaid adjustment of the pumping assembly. In the embodiment where the prime mover is an electric motor, the signal may be an electric signal.

The pressure measuring assembly may be arranged to provide a pressure difference feedback signal to the controller to provide the aforesaid information on the change in pressure across the orifice.

In a preferred embodiment, the controller converts the pressure difference feedback signal to the control signal.

The fluid flow control system may comprise a demand means for providing a demand for the fluid. Preferably, the demand means provides a demand signal relating to the rate of flow of fluid provided from the pumping assembly.

The controller may include a main comparator for comparing the demand signal with the pressure difference feedback signal to provide a control signal to control the prime mover driving the pump.

The fluid flow control system may further include a pump outlet pressure control arrangement comprising a pressure sensor to sense outlet pressure from the pumping assembly, and provide information on the aforesaid outlet pressure. In one embodiment, the information relating to the aforesaid outlet pressure may be provided to the controller for adjustment of the pumping assembly. The said adjustment may relate to the aforesaid outlet pressure.

The pump outlet pressure control arrangement may comprise a pressure compensator to modify the information relating to the aforesaid outlet pressure to a form usable by the pump assembly.

The pump outlet pressure control arrangement may provide an outlet pressure feedback signal to the controller, wherein the outlet pressure feedback signal provides the information on the outlet pressure of the pumping assembly.

The fluid flow control system may further comprise a combustion pressure control arrangement comprising a combustor pressure sensor to sense the pressure in a combustor of an engine, such as a gas turbine engine and provide information on the pressure in the combustor.

The information on the pressure in the combustor may be provided to the controller for adjustment of the pumping assembly. The said adjustment may relate to the aforesaid pressure in the combustor.

The combustor pressure control arrangement may provide a combustor pressure feedback signal to the controller, wherein the combustor pressure feedback signal provides the information on the combustor pressure.

The combustor pressure control arrangement may comprise a combustor pressure compensator to modify the information on the combustor pressure to a form usable by the pumping assembly.

The fluid flow control system may further comprise a pumping assembly speed control arrangement comprising a speed sensor to sense the speed of the pumping assembly and provide information on the aforesaid speed.

The information on the speed of the pumping assembly may be provided to the controller for adjustment of the pumping assembly, the said adjustment may relate to the aforesaid speed of the pumping assembly.

The pumping assembly speed control arrangement may provide a pumping assembly speed feedback signal to the controller, wherein the pumping assembly speed feedback signal provides the information on the speed of the pumping assembly. The pumping assembly speed control arrangement may comprise a speed compensator to modify the information on the speed of the pumping assembly to a form usable by the pumping assembly to a form usable by the pumping assembly.

The fluid flow control system may comprise at least one subsidiary comparator for comparing a primary control signal with one or more of the outlet pressure feedback signals, the combustor pressure feedback signal, and the speed feedback signal, and provide a subsidiary control signal for controlling the pumping signal.

According to another aspect of this invention, there is provided a method of controlling fluid flow, the said method comprising pumping a fluid to an orifice, measuring the pressure drop of the fluid across the orifice, providing information on the change in pressure across the orifice, processing the aforesaid information and adjusting the pumping assembly in accordance with the processed information to vary the rate of flow of the pump fluid.

In the preferred embodiment, the pumping assembly is a torque driven pumping assembly, and the method may comprise adjusting the torque of the torque driven pumping assembly in accordance with the processed information.

The method may further comprise modifying the aforesaid information, for example by a compensator to a form usable by the pump assembly.

Preferably, the method comprises providing a control signal from the controller to the pump assembly to effect the aforesaid adjustment of the pump assembly. In the embodiment where the motor is an electric motor, the method comprises providing an electrical signal to the pump assembly.

The stage of measuring the pressure difference across the orifice may comprise providing a pressure difference feedback signal to the controller to provide the aforesaid information on the change in pressure across the orifice.

Preferably, the method comprises converting the pressure difference feedback signal to the control signal by the controller.

The method may further comprise providing a demand signal relating to the rate of flow of fluid for the pumping assembly. The method may comprise comparing the demand signal with the pressure difference feedback signal to provide the control signal to control the prime mover driving the pump.

In one embodiment, the method may comprise sensing the outlet pressure at the pumping assembly and providing information on the aforesaid outlet pressure. The method may comprise providing the information on the aforesaid outlet pressure to the controller for adjustment of the pumping assembly. The said adjustment may relate to the aforesaid outlet pressure.

This embodiment may comprise modifying the information on the aforesaid outlet pressure to a form usable by the pumping assembly. The method may involve providing an outlet pressure feedback signal to the controller wherein the outlet pressure feedback signal provides information on the outlet pressure of the pumping assembly.

In one embodiment, the method may comprise sensing the pressure in a combustor of an engine, such as a gas turbine engine and providing information on the pressure in the combustor. The method may comprise providing the information on the pressure in the combustor to the controller for adjustment of the pumping assembly. The said adjustment may relate to the aforesaid pressure in the combustor.

A combustor pressure feedback signal may be provided to the controller, wherein the combustor pressure feedback signal provides the information on the combustor pressure. This embodiment may comprise modifying the information on the combustor pressure to a form usable by the pumping assembly.

In one embodiment, the method may comprise sensing the speed of the pumping assembly and providing information on the aforesaid speed. This embodiment may comprise providing the information on the aforesaid speed of the pumping assembly to the controller for adjustment of the pumping assembly. The said adjustment may relate to the aforesaid speed of the pumping assembly.

A pumping assembly speed feedback signal may be provided to the controller, wherein the pumping assembly speed feedback signal provides the information on the speed of the pumping assembly. This embodiment may comprise modifying the information on the speed of the pumping assembly to a form usable by the pumping assembly.

An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional side view of the upper half of the gas turbine engine;

FIG. 2 is a schematic diagram of a fluid flow control system.

Referring to FIG. 1, a gas turbine engine is generally indicated at 10 and comprises, in axial flow series, an air intake 11, a propulsive fan 12, an intermediate pressure compressor 13, a high pressure compressor 14, a combustor 15 a turbine arrangement comprising a high pressure turbine 16, an intermediate pressure turbine 17 and a low pressure turbine 18, and an exhaust nozzle 19.

The gas turbine engine 10 operates in a conventional manner so that air entering the intake 11 is accelerated by the fan 12 which produces two air flows: a first air flow into the intermediate pressure compressor 13 and a second air flow which provides propulsive thrust. The intermediate pressure compressor compresses the air flow directed into it before delivering that air to the high pressure compressor 14 where further compression take place.

The compressed air exhausted from the high pressure compressor 14 is directed into the combustor 15 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through and thereby drive the high, intermediate and low pressure turbines 16, 17 and 18, before being exhausted through the nozzle 19 to provide additional propulsive thrust. The high, intermediate and low pressure turbines 16, 17 and 18 respectively drive the high and intermediate pressure compressors 14 and 13 and the fan 12 by suitable interconnecting shafts.

Referring to FIG. 2, there is shown a fuel flow control system 20 for controlling the flow of fuel to a combustor 15. The fuel flow control system comprises a pumping assembly 22 for pumping fuel 23 to the combustor 15. The pumping assembly 22 comprises a torque driven pump 24 driven by an electric rotary motor 26. The motor 26 is actuated by electric drive circuits 28. The pump 24 pumps the fuel through an orifice 30.

The fuel flow control system 20 further comprises a pressure measuring assembly 32 for measuring the pressure drop of the flow of fuel across the orifice 30. The pressure measuring assembly 32 provides a pressure feedback signal 34 to a controller comprising a main comparator 36 and a main compensator 38.

The pressure feedback signal 34 is transmitted to the main compensator 38 to modify the pressure feedback signal 34 to a form which can be used by the pumping assembly 22. The signal passing from the main compensator 38 to the main comparator 36 is designated 34A.

The fuel flow control system 20 further includes demand means 40 for providing a demand signal 42 relating to the rate of fuel flow required by the combustor 15. The demand means 40 can be any suitable electronic and/or mechanical device connected to a control lever designed to produce predetermined signals on movement of the lever.

The demand signal 42 passes to a demand compensator 44 which modifies the demand signal to a form usable by the pumping assembly and the signal passing from the demand compensator 44 is designated 42A and passes to the main comparator 36.

The main comparator 36 compares the modified demand signal 42A with the modified pressure feedback signal 34A and provides a primary control signal 46. The primary control signal 46 passes to a control signal compensator 48 for further modification, if necessary. The signal transmitted from the control signal compensator 48 is designated 46A and can be passed to a subsidiary comparator 50, which will be explained below.

A subsidiary demand signal 52 passes from the subsidiary comparator 50 to a secondary control signal compensator 54 for modification and is then transmitted to the drive circuits to control the torque provided by the motor 26 to the pump 24, as shown by the arrow 56.

By providing suitable signals to control the torque driving the pump 24 in response to the change in pressure across the orifice 30, a greater degree of control can be maintained over the flow of fuel to the combustor 15.

If desired, further feedback loops shown in FIG. 2 can be provided for controlling other parameters of the pump or the flow of fuel. For example, a pressure sensor 58 can be provided to sense the pressure at the outlet of the pump. The pressure sensor 58 transmits a signal 60 to an outlet pressure compensator 61 for modification in the same way as described above. A modified signal 60A is transmitted to the subsidiary comparator 50, to modify the subsidiary control signal 52 which thus includes components that take into account the outlet pressure of the pump 24 and the change in pressure across the orifice 30.

If desired, a further feedback loop could be provided to take into account changes in pressure in the combustor 15. The second feedback loop would comprise a combustor pressure sensor 62 to measure the pressure in the combustor 15. The combustor pressure sensor 62 transmits a combustor pressure signal 64 to a combustor pressure compensator 65 for modification, and a modified combustor pressure signal 64A would be transmitted to the subsidiary comparator 50. The subsidiary control signal 52 would thus be modified in accordance with the modified combustor pressure control signal 64A.

If desired, the speed of the pumps could be controlled, and a pump speed sensor 66 could be mounted on the pump 24 to measure the speed of the pump 24. The pump speed sensor 66 would transmit a pump speed feedback signal 68 to a pump speed compensator 69 and a modified pump speed feedback signal 68A would be transmitted to the secondary comparator 50, such that the secondary control signal 52 would include a component relating to the pump speed and would thereby control the speed of the pump 24 in addition to the drive torque supplied thereto.

As used herein, the expression compensate is intended to refer to a modification process which could include conversion from one physical medium to another e.g. from current to torque or position to volts. The expression compensate may also refer to modification of the temporal behaviour of the system.

There is thus described an effective control system for controlling the torque on a pump thereby accurately controlling the flow of fuel to a combustor of a gas turbine engine.

The preferred embodiment described above, has the advantages that it can reduce pressure ripple through the combustor by modulating fuel flow to the combustor. Also the preferred embodiment provides a benefit of improved combustion stability.

Various modifications can be made without departing from the scope of the invention, for example other feedback loops could be provided, if desired.

The placement of the comparators could be modified to achieve the desired temporal behaviour of the system. In a further modification, the pressure difference sensor 32 could be replaced by separate pressure measurement devices on each side of the orifice 30, suitable comparison means could be provided to compare the difference in the measured pressure at the two pressure measurement devices. In this arrangement, where the pressure sensor 58 is used, it could provide a dual purpose. It will be appreciated that the length of pipe between the orifice 30 and the combustor 15 should be minimised. The orifice 30 could be defined by the combustor fuel nozzle or nozzles.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon. 

1. A fluid flow control system comprising a pumping assembly for pumping a fluid through an orifice, a pressure measuring assembly for measuring and providing information on the change in pressure across the orifice, and a controller for processing the aforesaid information to adjust the pump assembly in accordance with the aforesaid information and vary the rate of flow of the pumped fluid.
 2. A fluid flow control system according to claim 1 wherein the pumping assembly comprises a torque driven pumping assembly, and the controller is arranged to adjust the drive torque of the pump assembly in accordance with the aforesaid information on the change in pressure.
 3. A fluid flow control system according to claim 1 wherein the pumping assembly comprises a torque driven pump and a prime mover to create the torque for driving the pump, the prime mover having a rotatable component to provide the aforesaid torque to the pump.
 4. A fluid flow control system according to claim 1 wherein the fluid flow control system comprises a main compensator to modify the aforesaid information to a form usable by the pumping assembly.
 5. A fluid flow control system according to claim 1 wherein the controller provides a control signal to the pumping assembly to effect the aforesaid adjustment of the pumping assembly.
 6. A fluid flow control system according to claim 5 wherein the pressure measuring assembly is arranged to provide a pressure difference feedback signal to the controller to provide the aforesaid information on the change in pressure across the orifice, and the controller is arranged to convert the pressure difference feedback signal to the control signal.
 7. A fluid flow control system according to claim 5 wherein the fluid flow control system comprises a demand means for providing a demand for the fluid, the demand means providing a demand signal relating to the rate of flow of fluid provided from the pumping assembly.
 8. A fluid flow control system according to claim 7 wherein the controller includes a main comparator for comparing the demand signal with the pressure difference feedback signal to provide a control signal to control the prime mover driving the pump.
 9. A fluid flow control system according to claim 1 wherein the fluid flow control system further includes a pump outlet pressure control arrangement comprising a pressure sensor to sense outlet pressure from the pumping assembly and provide information on the aforesaid outlet pressure.
 10. A fluid flow control system according to claim 9 wherein the information relating to the aforesaid outlet pressure is provided to the controller for adjustment of the pumping assembly, the said adjustment relating to the aforesaid outlet pressure.
 11. A fluid flow control system according to claim 9 wherein the pump outlet pressure control arrangement comprises a pressure compensator to modify the information relating to the aforesaid outlet pressure to a form usable by the pump assembly.
 12. A fluid flow control system according to claim 9 wherein the pump outlet pressure control arrangement is configured to provide an outlet pressure feedback signal to the controller, wherein the outlet pressure feedback signal provides the information on the outlet pressure of the pumping assembly.
 13. A fluid flow control system according to claim 1 wherein the fluid flow control system further comprises a combustion pressure control arrangement comprising a combustor pressure sensor to sense the pressure in a combustor of an engine and provide information on the pressure in the combustor.
 14. A fluid flow control system according to claim 13 wherein the information on the pressure in the combustor is provided to the controller for adjustment of the pumping assembly, the said adjustment relating to the aforesaid pressure in the combustor.
 15. A fluid flow control system according to claim 13 wherein the combustor pressure control arrangement is configured to provide a combustor pressure feedback signal to the controller, wherein the combustor pressure feedback signal provides the information on the combustor pressure.
 16. A fluid flow control system according to claim 13 wherein the combustor pressure control arrangement comprises a combustor pressure compensator to modify the information on the combustor pressure to a form usable by the pumping assembly.
 17. A fluid flow control system according to claim 1 wherein the fluid flow control system further comprises a pumping assembly speed control arrangement comprising a speed sensor to sense the speed of the pumping assembly and provide information on the aforesaid speed.
 18. A fluid flow control system according to claim 17 wherein the information on the speed of the pumping assembly is provided to the controller for adjustment of the pumping assembly, the said adjustment relating to the aforesaid speed of the pumping assembly.
 19. A fluid flow control system according to claim 17 wherein the pumping assembly speed control arrangement is configured to provide a pumping assembly speed feedback signal to the controller, wherein the pumping assembly speed feedback signal provides the information on the speed of the pumping assembly.
 20. A fluid flow control system according to claim 17 wherein the pumping assembly speed control arrangement comprises a speed compensator to modify the information on the speed of the pumping assembly to a form usable by the pumping assembly to a form usable by the pumping assembly.
 21. A fluid flow control system according to claim 9 wherein the fluid flow control system comprises at least one subsidiary comparator for comparing a primary control signal with one or more of the outlet pressure feedback signals, the combustor pressure feedback signal, and the speed feedback signal, and provide a subsidiary control signal for controlling the pumping signal.
 22. A method of controlling fluid flow, the said method comprising pumping a fluid through an orifice, measuring the pressure drop of the fluid across the orifice, providing information on the change in pressure across the orifice, processing the aforesaid information and adjusting the pumping assembly in accordance with the processed information to vary the rate of flow of the pump fluid.
 23. A method according to claim 22 wherein the pumping assembly is a torque driven pumping assembly, and the method involves adjusting the torque of the torque driven pumping assembly in accordance with the processed information.
 24. A method according to claim 22 wherein the method further involves modifying the aforesaid information by a main compensator to a form usable by the pump assembly.
 25. A method according to claim 22 wherein the method involves providing a control signal from the controller to the pump assembly to effect the aforesaid adjustment of the pump assembly.
 26. A method according to claim 22 wherein the stage of measuring the pressure difference across the orifice comprises providing a pressure difference feedback signal to the controller to provide the aforesaid information on the change in pressure across the orifice.
 27. A method according to claim 26 wherein the method comprises converting the pressure difference feedback signal to the control signal by the controller.
 28. A method according to claim 26 wherein the method further comprises providing a demand signal relating to the rate of flow of fluid for the pumping assembly, the method comprising comparing the demand signal with the pressure difference feedback signal to provide the control signal to control a prime mover driving the pump.
 29. A method according to claim 22 wherein the method comprises sensing the outlet pressure at the pumping assembly and providing information on the aforesaid outlet pressure.
 30. A method according to claim 29 wherein the method comprises providing the information on the aforesaid outlet pressure to the controller for adjustment of the pumping assembly, the said adjustment relating to the aforesaid outlet pressure.
 31. A method according to claim 29 wherein the method comprises modifying the information on the aforesaid outlet pressure to a form usable by the pumping assembly.
 32. A method according to claim 29 wherein the method comprises providing an outlet pressure feedback signal to the controller wherein the outlet pressure feedback signal provides information on the outlet pressure of the pumping assembly.
 33. A method according to claim 22 wherein the method comprises sensing the pressure in a combustor of an engine, and providing information on the pressure in the combustor.
 34. A method according to claim 33 wherein the method comprises providing the information on the pressure in the combustor to the controller for adjustment of the pumping assembly, the said adjustment relating to the aforesaid pressure in the combustor.
 35. A method according to claim 33 wherein the method comprises providing a pressure feedback signal to the controller, wherein the combustor pressure feedback signal provides the information on the combustor pressure.
 36. A method according to claim 33 wherein the method comprises modifying the information on the combustor pressure to a form usable by the pumping assembly.
 37. A method according to claim 22 wherein the method comprises sensing the speed of the pumping assembly and providing information on the aforesaid speed.
 38. A method according to claim 37 wherein the method comprises providing the information on the aforesaid speed of the pumping assembly to the controller for adjustment of the pumping assembly, the said adjustment relating to the aforesaid speed of the pumping assembly.
 39. A method according to claim 37 wherein the method comprises providing a pumping assembly speed feedback signal to the controller, wherein the pumping assembly speed feedback signal provides the information on the speed of the pumping assembly.
 40. A method according to claim 37 wherein the method comprises modifying the information on the speed of the pumping assembly to a form usable by the pumping assembly. 